A puncture wound in the foot can be a life-threatening and career-ending injury for a horse. Once again, the seemingly rock-hard protection of the hoof capsule proves to be not as tough as it looks. Horses step on nails, cactus thorns, shards of wood and metal, fence stakes, shavings bag staples and any and every other thing in their paths. All those objects--and many more--are routinely revealed on the radiographs of lame horses, or removed from the frogs and heel bulbs of horses by farriers and veterinarians.A sharp object at just the right angle can penetrate the sole or frog and enter the foot, injuring vulnerable structures like the coffin joint, navicular bursa or deep digital flexor tendon.

Did Spectacular Bid lose the biggest race of his
life --and the Triple Crown--because he stepped
on a safety pin? It would take a special shoe
made by the legendary Jack Reynolds to
get him racing again.

Just ask Spectacular Bid. The racehorse hero of 1979 was on the fast track to win the Triple Crown. On the morning of the third leg of the Crown, the Belmont Stakes, the immensely popular gray stepped on a safety pin from his bandages in his stall, according to his trainer, who pulled the pin out and decided not to scratch the horse because he wasn’t lame. The rest, as they say, is history: Spectacular Bid did run in the Belmont that day, but the celebrated Derby and Preakness winner ran the full mile and a half without ever changing leads, according to his veterinarian. Maybe that pin left its mark after all.A foot wound lameness exam's goal is to avoid serious infection by collecting as much information as possible about the wound, what caused it, and when/how it occurred. Radiographic evaluation using contrast medium can be effective to show injury to the deep digital flexor tendon. Taking a radiograph with a probe inserted in the channel of the wound is sometimes an option, but many veterinarians prefer to radiograph the foot with the original offender still in place, so that the exact tract can be identified.Can puncture wounds have an impact? Just look in the history books: During World War I, veterinary records showed that 500 British horses per week were lost from service because of lameness traced to puncture wounds in their feet on the front in France.

Recent advances in treatment of puncture wounds
includes the use of sterile maggot debridement
therapy as used in this case
of a puncture wound in the front half of the foot.
(Scott Morrison case and image)

This little video was created by Dr. Rich Redding at North Carolina State University College of Veterinary Medicine. It's a set of MRIs used to diagnose a puncture wound that contacted the deep digital flexor tendon, but they have been speeded up for impact.

The 55 cases had variations in the amount of time that had passed since the injury had occurred. They also varied in the treatment and diagnostic regimen that had been employed. Several of the horses were euthanized because of the severe, irreparable damage done to structures inside the foot.The advantage of being able to see both soft tissue and bone in an MRI becomes particularly critical in evaluating a horse that has suffered a puncture wound. Urraca observed that 35 of the 55 horses had a visible tract, from 10 to 85mm long, in MR images. Of particular importance was that the tract’s visibility on an MR scan was more likely when the injury was less than one week old. In horses where the tract was visible, the extent of the injury and the structures affected was assessed readily. If the MR scan is done early, the short time lapse means that it will show “the tract filled with edema or hemorrhage, and you'll be able to follow it and look at the areas it has 'touched' for treatment,” Urraca said “You will prevent sepsis (infection) etc. If is too late--more than one week--you may only see the damage in the structures, and you cannot prevent anything any more.”

One reason why puncture wounds are so dangerous to horses is that an injury to the frog can be “invisible” to the naked eye. If a horse steps on a staple or metal stake, the frog tissue will simply close around the wound. An object can become embedded in the frog and not be visible at all. In other cases, a piece of wood or metal might break off and become embedded inside the frog. Wood fragments are difficult to view in diagnostic images of any type.In the 35 horses whose MR sessions included scanning in three planes, the transverse plane provided the best visualization of the lesion for viewing the deep digital flexor tendon and ligaments of the foot. This view was especially helpful in evaluating injuries that included hemorrhage within the foot, which shows up on the MR scan.

In the transverse plane, an MRI shows an injured foot 15 days after penetration. It is possible to see damage to the deep digital flexor tendon (arrow). The MR scan set would include progressive “slices” through the foot to show how far into the foot this injury extended. (Carolina Urraco image)

On the technical side, the paper commented that the highly sensitive T2*W sequence is the best to see hemorrhage in the foot, "ideally with an orientation parallel to the sole,” according to Urraca.Urraca’s study gives added weight to pleas from veterinarians for horse owners to consider any type of puncture wound a potential emergency. After the paper was published, Urraca commented how her research might affect horse owner actions if they find an object stuck in a horse’s foot.Advice from some clinicians is that horse owners should not remove the object, if at all possible. This is because the tract might not be visible on a radiograph, but the object would be.“There are two sides of the story,” Urraca commented via email, saying that it “is quite dangerous to leave it in place--it may get deeper, and it may tract contaminants--and also, as I found during my study, some horses step repeatedly on the nail until it finally lodges in a location. Therefore, leaving it in does not provide all the information, as there will be more than one tract.“If there is MRI available in the practice or close by, the clinician would need to remove the object to do the MRI,” she continued, “and the tract/s will be very easily seen if is done early enough, before the tract seals with granulation tissue."

MR scan of a puncture wound one day after the injury occurred. (Urraca study image)

MR scanning may make it possible for veterinarians to determine sooner if surgery is needed, and surgery may be more successful if it is done earlier instead of later.Horses aren’t always lame at the time of injury, and the injury is not always visible, but the potential consequences are immense. While most horses experience mild lameness, short-term infection and a full recovery to soundness, severe injuries benefit from earlier treatment or surgery and run a high risk of extended infection.Unlike “down” MR systems for equine imaging, Hallmarq “standing” MRI scanning does not require the horse to be under anesthesia to obtain the images; anesthesia may well be required if surgery is required, however.Are puncture wounds dramatic? Just ask anyone who was at the 2000 FEI Dressage World Cup final in The Netherlands.No puncture wound case was more dramatic than what occurred that day to Rozzie Ryan, who had traveled all the way from Australia with her horse, Excellent. On the way into the arena, the horse stepped on a roofing nail. He immediately went lame and was unable to perform his test. He left the arena and headed directly to the veterinary hospital at Utrecht University; there he had foot surgery, half a world away from home.A horse’s soundness, career, usefulness and even its life are at stake when a puncture wound in the foot is suspected. Every possible tool will and should be put to work to determine the nature and extent of the injury. Standing MRI has proven itself a valuable tool that may help ensure that horses who need surgery get it--and that possibly some who don’t need it will receive some good news sooner instead of later.

Disclosure of Material Connection: Hoofcare Publishing received direct compensation for writing this post. I have no material connection to the brands, products, or services that I have mentioned, other than Hoofcare Publishing. I am disclosing this in accordance with the Federal Trade Commission’s 16 CFR, Part 255: Guides Concerning the Use of Endorsements and Testimonials in Advertising.

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